Stimulating Damaged Spines Rewires Rats for Recovery

The nervous system adapts to severe injury when energized by electric pulses synced to muscle movements

3 min read
Stimulating Damaged Spines Rewires Rats for Recovery
Photo: Getty Images

human os icon

A promising new study shows that the nervous system can rewire itself—with a little help from neural engineers. 

For someone with a spinal cord injury, destroyed neurons act like a roadblock that prevents movement commands from traveling down the spinal cord and along the nerves. Although an injured person wills his fingers to grasp a cup, for example, the command never makes it to his hand.

But a study published today suggests that precisely controlled electrical stimulation can encourage the nervous system to create detours around that roadblock, allowing the command to get through. 

Neuroscientist Steve Perlmutter and his colleagues at the University of Washington devised a clever experiment using rats. The animals were first trained to perform a task in which they reached through narrow slots with their dominant forelimbs to grab food pellets. The rats were then given incomplete spinal cord injuries that almost totally paralyzed those limbs.

Next the rats were divided into three groups and, as if they were in physical therapy, trained again on the same task. The control group tried to perform the reach-and-grasp task unaided, the second group received random pulses of electrical stimulation in their spinal cords during the task, and the third group received stimulation pulses that were triggered by the rats’ attempts to move their immobilized limbs. 

img

Image: Perlmutter et al.
The head-mounted neurochip device recorded electrical signals from the muscles (called electromyographic or EMG activity) and triggered pulses of intraspinal microstimulation (ISMS).

The key advance here is that triggering technique. The researchers used a device called the neurochip-2, which recorded the weak electrical signal from the limb muscles and used that signal as the cue to initiate a pulse of electrical stimulation in the spinal cord. When the attempted muscle movement was synchronized with neural stimulation, the researchers believe that surviving neurons in the spinal cord formed new connections linking the muscles to the brain’s motor control region.  

What’s the underlying mechanism behind this remarkable repair work? I have just one word for you: neuroplasticity. Neural networks are malleable, and changing the patterns of connections between neurons can restore lost function. That’s why people who’ve suffered spinal cord injuries do rehab: They’re not trying to bring dead neurons back to life, but rather to teach the nervous system to work around them. However, people typically don’t recover much function with rehab alone. 

Perlmutter’s research suggests that adding electrical stimulation to rehab could provide a real boost. Over the course of the three-month study, the rats with neurochips showed dramatic improvement. The synchronized-stimulation rats ultimately performed the task 63 percent as well as they had before their injuries. Both the control group and the random-stimulation group performed about 30 percent as well as they did pre-injury.

Spectrum has covered “closed-loop” neurostimulation systems before, most notably in this feature article written by researchers from the companies Medronic, Cyberonics, and Neuropace. The authors described systems that used various bodily signals to trigger electrical pulses that countered epilepsy attacks and chronic pain. Such smart and responsive systems, which are now being used in humans, seem a clear step forward in electrical therapeutics

While the study from Perlmutter and his colleagues was conducted in rats, it points the way toward a new rehab strategy for people with spinal cord injuries. What’s more, it serves as a proof of principle for a strategy that may help people with other nervous system dysfunctions. By leveraging “the nervous system’s intrinsic capacity for reorganization and repair,” the authors write, electrical stimulation could help people regain lost motor abilities, perhaps, or bladder, bowel, or sexual function. 

The Conversation (0)

This CAD Program Can Design New Organisms

Genetic engineers have a powerful new tool to write and edit DNA code

11 min read
A photo showing machinery in a lab

Foundries such as the Edinburgh Genome Foundry assemble fragments of synthetic DNA and send them to labs for testing in cells.

Edinburgh Genome Foundry, University of Edinburgh

In the next decade, medical science may finally advance cures for some of the most complex diseases that plague humanity. Many diseases are caused by mutations in the human genome, which can either be inherited from our parents (such as in cystic fibrosis), or acquired during life, such as most types of cancer. For some of these conditions, medical researchers have identified the exact mutations that lead to disease; but in many more, they're still seeking answers. And without understanding the cause of a problem, it's pretty tough to find a cure.

We believe that a key enabling technology in this quest is a computer-aided design (CAD) program for genome editing, which our organization is launching this week at the Genome Project-write (GP-write) conference.

With this CAD program, medical researchers will be able to quickly design hundreds of different genomes with any combination of mutations and send the genetic code to a company that manufactures strings of DNA. Those fragments of synthesized DNA can then be sent to a foundry for assembly, and finally to a lab where the designed genomes can be tested in cells. Based on how the cells grow, researchers can use the CAD program to iterate with a new batch of redesigned genomes, sharing data for collaborative efforts. Enabling fast redesign of thousands of variants can only be achieved through automation; at that scale, researchers just might identify the combinations of mutations that are causing genetic diseases. This is the first critical R&D step toward finding cures.

Keep Reading ↓ Show less